The invention relates to casting equipment and a process for producing castings of the type in which the casting molds may comprise either permanent molds, that is, dies, or sand molds.
In the known low-pressure die casting process, the casting material is forced directly out of a hermetically sealed heatable pressurized container, with a slight increase in the gas pressure above the melt, through a casting tube into the casting mold located above the pressurized container. The feeding required during the solidification of the casting is assured by the melt that is under pressure and extends from the pressurized container on into the casting mold. The requisite stationary connection of the pressurized container, casting tube and casting mold over the entire process of casting and solidification of the casting leads to the following disadvantages:
each casting mold requires at least one separate pressurized container; PA1 laborious melt supply due to the pressurized furnace at the casting site and the corresponding melt holding operation; PA1 virtually exclusively, each casting mold requires its own mechanizing aid for casting production; PA1 labor costs and space requirements are high.
The advantages of these methods, such as bottom gating, nonturbulent mold filling, optimally variable solidification geometry, and exclusively non-feeder casting production, are overcome by the highly cost-intensive nature of these methods.
Moreover, in German Patent Disclosure DE 1 285 682, a low-pressure casting apparatus and the process for its operation are described in which a heated feeder pressure pot with a shutoff valve and a pressure piston rests between a casting mold and a casting tube connected rigidly to the furnace cover. After the mold has been filled and the melt confined in the feeder pressure pot via the shutoff valve, the pressure on the melt can be increased arbitrarily via a piston or a pressure unit simultaneously embodied as a shutoff slide, by the actuation of this piston or unit. The solidification of the casting occurs independently of the casting furnace.
A disadvantage here is that the casting molds are filled via a large-area feeder conduit, that the removal of the casting is dependent on the solidification of the residual metal in the heated feeder pressure pot, that the casting molds have to be placed together with the feeder pressure pot on the pressurized furnace and removed from it, and that for complicated casting geometries, many feeder conduits are required.
German Published, Non-Examined Patent Disclosure DE-OS 17 83 046 also describes an injection molding machine in which casting molds are filled with melt in a stationary casting station on an continuous basis. Here the casting molds are connected to the casting station, and separated from it again after the casting has solidified, by being raised and lowered. The overflow of melt takes place directly from the casting furnace into the casting mold via a feeder conduit. The supply of molten metal to the casting furnace is assured by a melt container positioned upstream of the casting station.
Since the injection molding machine has no feeder distributor container, castings that have to be made with a plurality of feeder conduits spaced apart from one another cannot be made with it. Another disadvantage is the supply of melt to the casting furnace; the molten melt must be fed from the smelting furnace into the holding container and from there into the casting furnace, which entails major losses of metal and energy.